PROJECT SUMMARY DR is a secondary complication of diabetes and a leading cause of blindness in the world. Although it is well known that DR is driven by ischemia, the current grading of DR severity is based only on structural alterations such as the presence of abnormal retinal microvasculature in non-proliferative DR and angiogenesis in proliferative DR. As a result, when their diagnosis is first received, most patients have already suffered from irreversible retinal functional impairment. DR develops through progressively increasing capillary non- perfusion, leading to insufficient blood supply to meet the metabolic demand of the inner retinal neurons. This causes retinal ischemia, which activates signaling pathways that promote angiogenesis and herald the proliferative phase of retinopathy. If not managed in a timely fashion, proliferative DR can ultimately lead to blindness. Therefore, non-invasive imaging of rMRO2 should improve our understanding of DR pathophysiology as well as significantly enhance our ability to diagnose and manage high-risk DR. Currently, laser panretinal photocoagulation (PRP) remains the standard-of-care intervention for proliferative DR, while anti-VEGF therapy is being aggressively explored as an alternative. In these treatments, the goal is to presumably reduce the overall retinal oxygen demand and ameliorate retinal ischemia or suppress the pathological angiogenesis. However, the exact mechanisms of both PRP and anti-VEGF effects have yet to be confirmed, as there are no human studies that document rMRO2 before and after these treatments. Hence, the failure of treating proliferative DR patients can only be gauged by monitoring the recurrence of angiogenesis, development of vitreous hemorrhage, or progressive retinal tractional detachment, all of which are associated with significant, and occasionally, permanent vision loss. Therefore, non-invasive monitoring of rMRO2 has the potential to significantly improve the management of proliferative DR. Prof. Hao F. Zhang?s group at Northwestern University demonstrated in 2013 that visible light optical coherence tomography (vis-OCT) can accurately quantify retinal sO2 and blood flow. In 2015, the Zhang lab further confirmed that vis-OCT can accurately quantify rMRO2 noninvasively in various rodent models of retinal ischemia and vis-OCT is safe for human use. Therefore, vis-OCT is the ideal candidate to investigate the role of rMRO2 dysregulation in early development, progression, and management of DR. Collaborating with the Zhang lab, Opticent Health?s goal is to translate vis-OCT from bench to bedside and to provide physicians with advanced clinical tools that can accurately and rapidly quantify rMRO2 in patients. Given the fact that vis-OCT is new and there has been limited clinical studies using vis-OCT, the crucial next step is to overcome obstacles that prevent vis-OCT from being smoothly integrated with clinical practices and to examine vis-OCT?s clinical impact. The proposed work addresses this need by developing robust algorithms to enable photographers with limited knowledge in optics and data processing to quickly and reliably measure patient?s rMRO2.